Copolymers as dewaxing additives

ABSTRACT

The invention relates to copolymers which are suitable for producing additives for solvent deparaffination of paraffin-containing mineral oil distillates and which consist of radically polymerized monomers of formulas A and B, wherein the radicals have the meaning cited in the description. The invention also relates to the use of said copolymers for the production of dewaxing additives.

FIELD OF THE INVENTION

The invention relates to copolymers or polymer mixtures which aresuitable for preparing additives for solvent deparaffinization ofparaffinic mineral oil distillates, to dewaxing additives preparedtherefrom and also to their use in the solvent deparaffinization ofparaffinic mineral oil distillates.

Prior Art

U.S. Pat. No. 4,451,353 describes mixtures of a poly-C₁₀-C₂₈-alkylacrylate and a poly-n-alkyl methacrylate (C₁₀-C₂₀) as dewaxingadditives. However, reference is made to the exclusive use of linearpolyalkyl methacrylates as mixing components.

DE-A-3933376 demonstrated that when polyalkyl methacrylate mixingcomponents having high degrees of branching of the alkyl radicals areused, improved effectiveness and more marked synergistic effects occurthan in linear systems.

Tanasescu et al. (Rev. Chim. (Bucharest) 1998, 49(9), 593-597) mentionedthe evaluation of copolymers of C₁₀₋₁₈, methacrylates and styrene asdewaxing aids in methyl ethyl ketone/toluene mixtures. However,reference is made to the worsened effectiveness of the styrenic polymersin comparison to the purely methacrylate-based additives and this isexplained by a “dilution effect” with regard to the effective alkyl sidegroups. Polymers having side chains >C₁₈, i.e. behenyl(meth)-acrylatesamong others, are not mentioned.

Object and Solution:

It is an object of the present invention to provide copolymers orpolymers having improved effectiveness in the solvent deparaffinizationof paraffinic mineral oil distillates, in particular when used indifferent feedstocks and using different solvent systems. In particular,the more effective dewaxing aids should be provided very substantiallyon the basis of existing starting materials which should cause nosubstantial changes in the performance of the deparaffinizationtechnology of crude oils or crude oil products.

This object and further objects that are not specified explicitly areachieved by copolymers which consist of free-radically polymerizedmonomers of the following formulae A and B:

where

-   R¹═H or CH₃,-   R²=phenyl, benzyl, naphthyl, anthranyl, phenanthryl, N-pyrrolidonyl,    N-imidazolyl, 2-pyridyl, 4-pyridyl or an alkyl-substituted aromatic    substituent or-   R²═COOR³ where R³═H or R³ is a linear or branched alkyl radical of    C₁-C₁₀-   or R³ is a heteroatom-substituted radical —(CH₂)_(n)X where X═OH or    X═N(R⁴)₂ where n=1-10 and R⁴ is in each case independently H or    R⁴═C₁-C₄-alkyl-   or R³ is —(CH₂CH₂O)_(m)R⁵ where m=1-90 and R⁵═H or R⁵═C₁-C₁₈ or R³    is a benzyl, phenyl or cyclohexyl radical-   or R²═CONHR⁶ where R⁶═H or R⁶ is a linear or branched alkyl radical    of C₁-C₁₀ or R⁶ is a heteroatom-substituted radical —(CH₂)_(n)X    where X═OH or X═N(R⁴)₂ where n=1-10 and R⁴ is in each case    independently H or R⁴═C₁-C₄-alkyl;    where R⁷═H or CH₃    and the R⁸ radical ═H or linear or branched alkyl radicals of    C₁₂-C₄₀.

Further solutions which are likewise suitable and also suitable uses ofthe copolymers or polymers according to the invention are described inthe subclaims.

Implementation:

The monomers of the formula A:

where

-   R³═H or CH₃,-   R² phenyl, benzyl, naphthyl, anthranyl, phenanthryl, N-pyrrolidonyl,    N-imidazolyl, 2-pyridyl, 4-pyridyl or an alkyl-substituted aromatic    substituent or-   R²═COOR³ where R³═H or R³ is a linear or branched alkyl radical of    C₁-C₁₀-   or R³ is a heteroatom-substituted radical —(CH₂)_(n)X where X═OH or    X═N(R⁴)₂ where n=1-10 and R⁴ is in each case independently H or    R⁴═C₁-C₄-alkyl-   or R³ is —(CH₂CH₂O)_(m)R⁵ where m=1-90 and R⁵═H or R⁵═C₁-C₁₈-alkyl    or R³ is a benzyl, phenyl or cyclohexyl radical-   or R²═CONHR⁶ where R⁶═H or R⁶ is a linear or branched alkyl radical    of C₁-C₁₀-   or R is a heteroatom-substituted radical —(CH₂)_(n)X where X═OH or    X═N(R⁴)₂, n=1-10 and R is in each case independently H or    R⁴═C₁-C₄-alkyl are, for example, styrene, alpha-methylstyrene,    alpha- or beta-vinylnaphthalene, alpha- or beta-vinylphenanthrene,    N-vinylpyrrolidone, 2- or 4-vinylpyridine or their, for example    alkyl-substituted, derivatives.

The compositions from which the (co)polymers according to the inventionare obtained comprise in particular (meth)acrylates, maleates and/orfumarates which have different alcohol radicals. The term(meth)acrylates encompasses methacrylates and acrylates and alsomixtures of both. These monomers are well known. The alkyl radical maybe linear, cyclic or branched.

Examples include (meth)acrylates, fumarates and maleates which arederived from saturated alcohols, such as methyl(meth)acrylate,ethyl(meth)acrylate, n-propyl(meth)acrylate, isopropyl(meth)acrylate,n-butyl(meth)acrylate, tert-butyl(meth)acrylate andpentyl(meth)acrylate;

-   cycloalkyl(meth)acrylates, such as cyclopentyl(meth)acrylate;-   (meth)acrylates which are derived from unsaturated alcohols, such as    2-propynyl(meth)acrylate, allyl (meth)acrylate and    vinyl(meth)acrylate.

Further constituents which may be present in the compositions to bepolymerized include: (meth)acrylates, fumarates and maleates which arederived from saturated alcohols, such as hexyl(meth)acrylate,2-ethylhexyl(meth)acrylate, heptyl(meth)acrylate,2-tert-butylheptyl(meth)acrylate, octyl(meth)acrylate,3-isopropylheptyl(meth)acrylate, nonyl (meth)acrylate,decyl(meth)acrylate, undecyl(meth)acrylate,5-methylundecyl(meth)acrylate, dodecyl (meth)acrylate,2-methyldodecyl(meth)acrylate, tridecyl (meth)acrylate,5-methyltridecyl(meth)acrylate, tetradecyl(meth)acrylate,pentadecyl(meth)acrylate;

-   (meth)acrylates which are derived from unsaturated alcohols, e.g.    oleyl(meth)acrylate;-   cycloalkyl(meth)acrylates such as 3-vinylcyclohexyl (meth)acrylate,    cyclohexyl(meth)acrylate, bornyl (meth)acrylate; and also the    corresponding fumarates and maleates.

Examples of further components include (meth)acrylates which are derivedfrom saturated alcohols such as hexadecyl(meth)acrylate,2-methylhexadecyl(meth)acrylate, heptadecyl(meth)acrylate,5-isopropyl-heptadecyl (meth)acrylate, 4-tert-butyloctadecyl(meth)acrylate, 5-ethyloctadecyl(meth)acrylate, 3-isopropyloctadecyl(meth)acrylate, octadecyl(meth)acrylate, nonadecyl(meth)acrylate,eicosyl(meth)acrylate, cetyleicosyl(meth)acrylate, stearyleicosyl(meth)acrylate, docosyl(meth)acrylate and/or eicosyl-tetratriacontyl(meth)acrylate;

-   cycloalkyl(meth)acrylates such as    2,4,5-tri-t-butyl-3-vinylcyclohexyl(meth)acrylate,    2,3,4,5-tetra-t-butylcyclohexyl (meth)acrylate; oxiranyl    methacrylates such as 10,11-epoxyhexadecyl methacrylate; and also    the corresponding fumarates and maleates.

Longer-chain (meth)acrylates are formed, for example, from acrylicesters of C10-C40-alkanols or of acrylic esters of C18-C24-alkanols, forexample of the behenyl alcohol type.

Particular emphasis is given to esters of (meth)acrylic acid withalkanols having C₁₂-C₁₈-hydrocarbon radicals, for example having anaverage carbon number of 14, for example mixtures of DOBANOL® 25L(product of Shell AG) and tallow fatty alcohol, and also mixtures oftallow fatty alcohol and other alcohols, for example i-decyl alcohol.

The ester compounds having a long-chain alcohol radical can be obtained,for example, by reacting (meth)acrylates, fumarates, maleates and/or thecorresponding acids with long-chain fatty alcohols, which generallyresults in a mixture of esters, for example (meth)acrylates havingalcohol radicals of different chain lengths. Among others, these fattyalcohols include Oxo Alcohol® 7911 and Oxo Alcohol® 7900, Oxo Alcohol®1100 from Monsanto; Alphanol® 79 from ICI; Nafol® 1620, Alfol® 610 andAlfol® 810 from Condea; Epal® 610 and Epal® 810 from Ethyl Corporation;Linevol® 79, Linevol® 911 and Dobanol® 25L from Shell AG; Lial 125 fromAugusta® Milan; Dehydad® and Lorol® from Henkel KGaA and also Linopol®7-11 and Acropol® 91 Ugine Kuhlmann.

Among the ethylenically unsaturated ester compounds, particularpreference is given to the (meth)acrylates over the maleates andfumarates.

Components which are likewise suitable includehydroxyalkyl(meth)acrylates such as 3-hydroxypropyl methacrylate,3,4-dihydroxybutyl methacrylate, 2-hydroxyethyl methacrylate,2-hydroxypropyl methacrylate, 2,5-dimethyl-1,6-hexanediol(meth)acrylate, 1,10-decanediol (meth)acrylate;aminoalkyl(meth)acrylates such asN-(3-dimethylaminopropyl)methacrylamide, 3-diethylaminopentylmethacrylate, 3-dibutylaminohexadecyl(meth)acrylate;

-   nitriles of (meth)acrylic acid and other nitrogen-containing    methacrylates such as N-(methacryloyloxyethyl)diisobutylketimine,    N-(methacryloyloxyethyl)dihexadecylketimine,    methacryloylamidoacetonitrile,    2-methacryloyloxyethylmethylcyanamide, cyanomethyl methacrylate;-   aryl(meth)acrylates such as benzyl methacrylate or phenyl    methacrylate where the aryl radicals may each be unsubstituted or up    to tetrasubstituted;-   carbonyl-containing methacrylates such as 2-carboxyethyl    methacrylate, carboxymethyl methacrylate, oxazolidinylethyl    methacrylate, N-(methacryloyloxy)formamide, acetonyl methacrylate,    N-methacryloylmorpholine, N-methacryloyl-2-pyrrolidinone,    N-(2-methacryloyloxyethyl)-2-pyrrolidinone,    N-(3-methacryloyloxypropyl)-2-pyrrolidinone,    N-(2-methacryloyloxypentadecyl)-2-pyrrolidinone,    N-(3-methacryloyloxyheptadecyl)-2-pyrrolidinone;-   glycol dimethacrylates such as 1,4-butanediol methacrylate,    2-butoxyethyl methacrylate, 2-ethoxyethoxymethyl methacrylate,    2-ethoxyethyl methacrylate;-   methacrylates of ether alcohols, such as tetrahydrofurfuryl    methacrylate, vinyloxyethoxyethyl methacrylate, methoxyethoxyethyl    methacrylate, 1-butoxypropyl methacrylate,    1-methyl-(2-vinyloxy)ethyl methacrylate, cyclohexyloxymethyl    methacrylate, methoxymethoxyethyl methacrylate, benzyloxymethyl    methacrylate, furfuryl methacrylate, 2-butoxyethyl methacrylate,    2-ethoxyethoxymethyl methacrylate, 2-ethoxyethyl methacrylate,    allyloxymethyl methacrylate, 1-ethoxybutyl methacrylate,    methoxymethyl methacrylate, 1-ethoxymethyl methacrylate,    ethoxymethyl methacrylate, methacrylates of halogenated alcohols    such as 2,3-dibromopropyl methacrylate, 4-bromophenyl methacrylate,    1,3-dichloro-2-propyl methacrylate, 2-bromoethyl methacrylate,    2-iodoethyl methacrylate, chloromethyl methacrylate;-   oxiranyl methacrylates such as 2,3-epoxybutyl methacrylate,    3,4-epoxybutyl methacrylate, 10,11-epoxyundecyl methacrylate,    2,3-epoxycyclohexyl methacrylate; glycidyl methacrylate;-   phosphorus-, boron- and/or silicon-containing methacrylates such as    2-(dimethylphosphato)propyl methacrylate,    2-(ethylenephosphito)propyl methacrylate, dimethylphosphinomethyl    methacrylate, dimethylphosphonoethyl methacrylate,    diethylmethacryloyl phosphonate, dipropylmethacryloyl phosphate,    2-(dibutylphosphono)ethyl methacrylate,    2,3-butylenemethacryloylethyl borate,    methyldiethoxymethacryloylethoxysilane, diethylphosphatoethyl    methacrylate;-   sulphur-containing methacrylates such as ethylsulphinylethyl    methacrylate, 4-thiocyanatobutyl methacrylate, ethylsulphonylethyl    methacrylate, thiocyanatomethyl methacrylate, methylsulphinylmethyl    methacrylate, bis(methacryloyloxyethyl)sulphide;-   trimethacrylates such as trimethyloylpropane trimethacrylate;-   vinyl halides, for example vinyl chloride, vinyl fluoride,    vinylidene chloride and vinylidene fluoride;-   heterocyclic (meth)acrylates such as 2-(1-imidazolyl)ethyl    (meth)acrylate, 2-(4-morpholinyl)ethyl(meth)acrylate and    1-(2-methacryloyloxyethyl)-2-pyrrolidone;-   vinyl esters such as vinyl acetate;-   styrene, substituted styrenes having an alkyl substituent in the    side chain, for example α-methylstyrene and α-ethylstyrene,    substituted styrenes having an alkyl substituent on the ring, such    as vinyltoluene and p-methylstyrene, halogenated styrenes, for    example monochlorostyrenes, dichlorostyrenes, tribromostyrenes and    tetrabromostyrenes;-   heterocyclic vinyl compounds such as 2-vinylpyridine,    3-vinylpyridine, 2-methyl-5-vinylpyridine, 3-ethyl-4-vinylpyridine,    2,3-dimethyl-5-vinylpyridine, vinylpyrimidine, vinylpiperidine,    9-vinylcarbazole, 3-vinylcarbazole, 4-vinylcarbazole,    1-vinylimidazole, 2-methyl-1-vinylimidazole, N-vinylpyrrolidone,    2-vinylpyrrolidone, N-vinylpyrrolidine, 3-vinylpyrrolidine,    N-vinylcaprolactam, N-vinylbutyrolactam, vinyloxolane, vinylfuran,    vinylthiophene, vinylthiolane, vinylthiazol-es and hydrogenated    vinylthiazoles, vinyloxazoles and hydrogenated vinyloxazoles;-   vinyl and isoprenyl ethers;-   maleic acid and maleic acid derivatives, for example mono- and    diesters of maleic acid, maleic anhydride, methylmaleic anhydride,    maleimide, methylmaleimide; fumaric acid and fumaric acid    derivatives, for example mono- and diesters of fumaric acid;-   dienes, for example divinylbenzene.

Very particularly preferred mixtures comprise methyl methacrylate, butylmethacrylate, lauryl methacrylate, stearyl methacrylate and/or styrene.

These components may be used individually or as mixtures.

The components of the formula B:

where R⁷═H or CH₃and the R⁶ radical ═H or linear or branched alkyl radicals of C₁₂-C₄₀,preferably alkyl radicals of chain length C₁₆-C₃₂ and in particularalkyl radicals of chain length C₁₈-C₂₄,are relatively long-chain (meth)acrylates known per se, as alreadydescribed hereinabove.

They are composed, for example, of (meth)acrylic esters ofC₁₂-C₄₀-alkanols or of (meth)acrylic esters of C₁₆-C₃₂-alkanols or ofC₁-C₂₄-alkanols, for example of the behenyl alcohol type.

Mention is also made of esters of (meth)acrylic acid with alkanolshaving C₁₂-C₁₈-hydrocarbon radicals, for example having an averagecarbon number of 14, for example mixtures of DOBANOL® 25L (product fromShell AG) and tallow fatty alcohol, and also mixtures of tallow fattyalcohol and other alcohols, for example i-decyl alcohol.

The polymerization of the monomers may likewise be carried out in amanner known per se.

Advantageously, the free-radical polymerization is carried out in asolvent compatible with the substrate to be deparaffinized, for examplein mineral oil. Customary polymerization initiators are used, forexample peroxy compounds, in particular peresters, e.g. tert-butylperpivalate, tert-butyl peroctanoate, tertbutyl perbenzoate, amongothers, in the customary amounts, for example 0.1 to 5% by weight,preferably 0.3 to 1% by weight, based on the monomers (cf. Th. Völker,H. Rauch-Puntigam, Acryl- und Methacryl-verbindungen, Springer-Verlag1967).

Likewise in a manner known per se, molecular weight regulators may beadded to the mixtures, in particular mercaptans, e.g. dodecylmercaptan,in the customary amounts, for example 0.01 to 2% by weight, based on themonomers.

Advantageously, operation is effected under a protective gas, forexample CO₂, nitrogen or argon.

An advantageous procedure is to dissolve the monomers in the solvent ina suitable polymerization vessel equipped with a stirrer, optionallytogether with regulator and initiator and to initially degas, forexample by means of CO₂ snow, and then to heat.

A starting point may be, for example, 80° C.±10° C. The initiator mayalso in some cases be added to the heated mixture. Optionally, furthermonomer and initiator and also regulator are metered in. The temperaturegenerally rises further, for example to 140° C.±10° C. Optionally,conditions suitable for the continued polymerization may be obtained byintroducing heat and/or adding further initiator. The overallpolymerization time is generally below 12 hours.

In an advantageous embodiment, the (co)polymers according to theinvention comprise a proportion by weight of monomer A in the totalweight of the copolymer of 0.1-70%, preferably 0.5-50% and morepreferably 5-30%.

The monomer A may advantageously consist of one or more of the monomersstyrene, butyl methacrylate, methyl methacrylate or 2-ethylhexylmethacrylate.

In a likewise advantageous embodiment, at least 50% of the monomers Bcontain alkyl radicals R⁸ of chain length greater than or equal to C₁₆.

In addition to one or more of the copolymers previously described, thepolymer mixture according to the invention may also comprise one or morefurther homo- or copolymers which are polyalkyl methacrylates and havealkyl substituents of chain length C₁-C₂₄ or of chain length C₁₂-C₁₈.The compounds already described may be used for this purpose.

In this polymer mixture, the ratio of the copolymers and the furtherhomo- or copolymers is advantageously 1:20 to 20:1, preferably 1:10 to10:1 and more preferably 1:5 to 5:1.

In an advantageous embodiment, any further homo- or copolymer containedin the polymer mixture is a polyalkyl methacrylate which contains up to20% by weight of C₁-C₁₀-methacrylates.

The molecular weight of the copolymers or polymers used is between10,000 and 3,000,000 g/mol, between 100,000 and 1,500,000 g/mol, between150,000 and 800,000 g/mol or between 200,000 and 500,000 g/mol.

The determination of the molecular weight may be carried out by means ofgel permeation chromatography (cf. Kirk-Othmer, Encyclopedia of ChemicalTechnology, 3rd Ed., Vol. 18, pg. 209, 749, J. Wiley 1982).

The polymer components may be prepared in a manner known per se in abatch process by introducing all of the monomers used into theinitial-charge, or in a feed process. The preparation may also beeffected in a feed process by synthesizing at least one of the polymersof the polymer mixture using an increased concentration of at least oneof the monomers used in the initial monomer charge in comparison to theother monomer types used with the aim of preparing a polymer mixture inwhich different polymers are present with regard to the monomercomposition.

The copolymers or polymer mixtures according to the present inventionserve to prepare dewaxing additives, optionally with the addition offurther customary additives for dewaxing additives.

In particular, the dewaxing additives may be a solution of thecopolymers or of the polymer mixture in an oil of the paraffinic ornaphthenic type or else in an organic solvent.

In this case, the organic solvent in a preferred embodiment is toluene,xylene and/or naphtha.

With regard to the wax-containing substrates based on crude oil andsuitable for deparaffinization, no definite limits to the process can berecognized, although, from a practical standpoint, useful substrates arein particular wax-containing distillate oils, in particular those havinga boiling range of approx. 300 to approx. 600° C., a density of approx.0.08-0.09 g/cc at 15° C., a viscosity of approx. 10-20 cSt/100° C., apour point of approx. 30-50° C. and a wax content (dry) of from approx.10 to approx. 25% by weight.

Particular importance attaches to distillate oils of those fractionswhich include lubricants and speciality oils in the 300-600° C. boilingrange, in particular those having an average boiling point of approx.400-450° C.

The solvents used for solvent deparaffinization according to theinvention likewise correspond to those used customarily. These are, forexample:

-   aliphatic hydrocarbons having a boiling point <150° C. at    atmospheric pressure, and among these the self-cooling gases such as    propane, propylene, butane, pentane and also isooctane, aromatic    hydrocarbons, for example toluene and xylene, ketones, for example    acetone, dimethyl ketone, methyl ethyl ketone, methyl propyl ketone,    methyl isobutyl ketone, optionally also halogenated hydrocarbons    such as methylene chloride or dichloroethane, or N-alkylpyrrolidones    such as N-methylpyrrolidone or N-ethylpyrrolidone.

Mixtures of solvents are also advantageous, for example of ketones andaromatic hydrocarbons such as methyl ethyl ketone/toluene or methylisobutyl ketone/toluene.

The solvent S in the process according to the invention is added in thecustomary amounts, for example 0.5-10 parts by volume, preferably 2-7parts by volume, based on the substrate to be deparaffinized.

When a dewaxing additive is used for solvent deparaffinization ofparaffinic mineral oil distillates, the addition rate of the copolymeror of the polymer mixture in the dewaxing process is 0.005-0.5% ppm, inparticular 0.01-0.3% ppm or 0.05-0.18% ppm.

Unexpectedly, it has been found that copolymers of alkyl acrylates, inparticular behenyl acrylate (═C₁₈₋₂₄), and styrene are more effectivedewaxing aids than corresponding styrene-free polymers in differentfeedstocks and using different solvent systems. The latter systems arethe state of the art. This is true both for the comparison betweenindividual components, i.e. poly-behenyl acrylate-co-styrene withpolybehenyl acrylate, and for the comparison between styrenic andstyrene-free mixed components. A polybehenyl-co-styrene/polymethacrylatemixed system is thus more effective than a polybehenyl/polymethacrylatemixture. Improvements in comparison with the existing mixed componentsare revealed in comparisons with mixed systems comprising linearpolyalkyl methacrylates as described in U.S. Pat. No. 4,451,353 but alsoin the comparison with mixed systems comprising branched polyalkylmethacrylates.

It has likewise been found that the incorporation of other monomers inaddition to styrene into copolymers with behenyl acrylate also leads tonovel dewaxing additives which, just as unexpectedly as the styrenesystems, lead to improved dewaxing results in comparison to the priorart. For example, copolymers composed of behenyl acrylate and eithern-butyl methacrylate, isononyl methacrylate or benzyl methacrylate werebetter in every respect than polybehenyl acrylate polymers.

The statements made are manifested in the examples describedhereinbelow, in particular with the aid of the filtration ratesmeasured.

Example 9 shows that a mixture of the styrene/behenyl acrylate copolymerP1 with the polymethacrylate P7 (P7 as a C₁₂-C₁₈-polymethacrylate havinglinear side chains) in a 600N feedstock of a European refineryfacilitated shorter filtration times in comparison with the mixture ofthe styrene-free analogue C1 with polymer P7. Equally, a mixture of P1and P8 (P8 is a C₁₂-C₁₈ polymethacrylate having more significantlybranched side chains than P7) in this feedstock was distinctly betterthan the mixture of the styrene-free C1 with P8 corresponding to theprior art. A further example which demonstrates the improvedeffectiveness of a styrenic additive is provided by a mixture of P1 andthe C₁₆-C₁₈ polymethacrylate P6 in comparison to the comparative sampleconsisting of a mixture of C1 and P6, likewise in European 600Nfeedstock. Equally, it can be clearly recognized in Example 11 that theindividual component P1 also provided shorter filtration times incomparison to the comparative sample C1.

The finding obtained on styrenic systems was additionally substantiatedwith the aid of investigations in two alternative feedstocks (seeExamples 10 and 11). Dewaxing studies carried out in n-heptane in a 500Nfeedstock of a Thai refinery (Example 10) demonstrate that filtrationtimes resulting from 3:8 mixtures of P1 with P6 or 3:8 mixtures of P1with P7 were in both cases shorter in comparison to a mixture consistingof C1 and C6. Example 11 repeats a dewaxing study carried out with a300N feedstock of a refinery in South America. This example demonstratesthat the principle illustrated here can be extended not only toadditional feedstocks, but also to alternative solvent systems.Filtration experiments in methyl ethyl ketone/toluene show that a P1/P6mixture leads to improved filtration times in comparison to a mixture ofC1 and C6.

Example 12 carried out in n-heptane in the same 600N feedstock which wasused in Example 9 shows that not only copolymers of styrene and behenylacrylate, but also copolymers of other monomer types and behenylacrylate are more effective than polybehenyl acrylates. Although itcould be seen that the styrenic additive P1 led to the best results, then-butyl methacrylate/behenyl acrylate copolymer was hardly any worse.Dewaxing studies using the benzyl methacrylate/behenyl acrylatecopolymer P2 and also with the isononyl methacrylate/behenyl acrylatecopolymer P5 were likewise distinctly more successful in comparison toresults obtained with the behenyl acrylate polymer C1.

When preparing lubricants, the wash distillates from vacuum distillationof crude oil are initially freed of aromatics and heterocycles bysolvent extraction. This improves the aging stability and the viscosityindex. The raffinates still contain large amounts of paraffin wax andhave correspondingly high pour points. Therefore, the majority of theparaffin is removed by solvent deparaffinization. To this end, theraffinate is admixed with a suitable solvent, for example methyl ethylketone-toluene and dichloroethane-dichloromethane mixtures or elsepropane. Then the mixture is cooled to temperatures of below −20° C. andthe paraffin wax which has crystallized out is removed by a drum filter.Paraffin crystal platelets, as are formed without the addition ofadditives, block the filters and incorporate large amounts of oil (slackwax). As a consequence, the filtration rate in deparaffinization isoften low and the oil yield is not optimum. Variation of the processparameters such as cooling rate, composition of the solvent mixture,filtration temperature and degree of dilution may be used to counteractthese effects. However, process optimization can also be achieved byusing polymeric dewaxing aids. Such dewaxing aids influence the size andshape of the paraffin crystals, so that compact structures are formedwhich form a filtercake which is porous and permeable to the solvent-oilmixture. Filtration rate and oil yield can be increased considerably inthis way.

The literature discloses that in particular compact agglomerates of manysmall paraffin crystals which grow epitaxially, for example on vesiclesof polyalkyl acrylates, form filtercakes of ideal texture and highporosity.

Polyalkyl methacrylates and polyalkyl acrylates which contain no othertypes of methacrylate or acrylate monomer are described in detail asdewaxing aids both in patents and in other literature. Both individualcomponents and mixtures of different poly(meth)acrylate systems areillustrated as effective dewaxing aids.

Implementation of a Laboratory Filtration Test for Determining theFiltration Rate:

In order to be able to carry out a selection of suitable polymers in thelaboratory, a laboratory filtration apparatus has been developed whichallows the measurement of oil yield and filtration rate. The filtrationrate especially proved to be an important criterion for selectingsuitable dewaxing aids. The filtration apparatus consists of a steelfilter having a lid and cooling jacket and is cooled with the aid of acryostat in circulation. The filter cloth used is from thedeparaffinization plant of the refinery. The filter volume is 100 ml.The filter is connected via a glass attachment having a two-way tap to ameasuring cylinder. A defined vacuum may be applied to the filtrationapparatus by means of a rotary vane oil pump, a pressure-reducing valveand a manometer. The mineral oil distillate to be deparaffinized isadmixed while hot, typically at 70° C., but in every case above thecloud point, with the deparaffinizing solvents and also the dewaxingaids and stirred until a clear solution results. The temperature controlis then used to cool at a defined rate to the desired filtrationtemperature. The filter is precooled to this temperature.

All filtration conditions such as solvent:feedstock ratio, ratio of thesolvents in the case of the use of solvent mixtures, cooling rates andfiltration temperatures correspond to those conditions used in theparticular refinery.

After the filtration temperature is obtained, the mixture is transferredto the precooled filter and the vacuum is applied. Operation istypically effected at a subatmospheric pressure of from 300 to 700 mbar.The filtration volume is then determined as a function of time. Thefiltration is over when no more liquid passes through the filter cloth.

The additives were used in the dewaxing experiments as polymer solutionsin oil as prepared in the examples which follow. Alternatively, othersolvent types may find use as support media of the dewaxing aids withoutany differences in effectiveness being detected thereby.

EXAMPLES

The behenyl acrylate used was obtained from Sidobre Sinova and useddirectly without further purification. A typical carbon numberdistribution in the behenyl radical is C₁₈(40.0-46.0%), C₂₀(8.0-14.0%),C₂₂(42.0-48.0%). The source of the other methacrylate monomer types isspecified in the preparation methods which follow. The viscosities arereported according to η_(sp)/c (CHCl₃, 20° C.).

Example 1 Preparation of a Copolymer of Behenyl Acrylate and Styrene P1

In a three-necked flask equipped with a sabre stirrer and a refluxcondenser, 306 g of behenyl acrylate (e.g. 45% behenyl acrylate fromSidobre Sinova), 34 g of styrene, 60 g of 100 N oil and 0.34 g ofdodecylmercaptan are initially charged under a nitrogen protective gasatmosphere and heated to 80° C. 0.64 g of t-butyl perpivalate and 0.38 gof t-butyl perbenzoate are subsequently added, in order to initiate thepolymerization. 2 hours after reaching the peak temperature, 0.68 g oft-butyl perbenzoate are added and polymerization is continued at 130° C.for 10-12 hours.

-   M_(w) (GPC, PMMA calibration)=490,000 g/mol-   η_(sp)/c (CHCl₃, 20° C.)=50.7 ml/g-   Thickening action (4.5% in a 150 N oil): 12.68 mm²/s

Example 2 Preparation of a Copolymer of Behenyl Acrylate and BenzylMethacrylate P2

In a three-necked flask equipped with a sabre stirrer and a refluxcondenser, 306 g of behenyl acrylate (e.g. 45% behenyl acrylate fromSidobre Sinova), 34 g of benzyl methacrylate (manufacturer: Röhm GmbH &Co. KG, Darmstadt), 60 g of 100 N oil and 0.51 g of dodecylmercaptan areheated to 80° C. 0.64 g of t-butyl perpivalate and 0.38 g of t-butylperbenzoate are subsequently added, in order to initiate thepolymerization. 2 hours after reaching the peak temperature, 0.68 g oft-butyl perbenzoate are added and polymerization is continued at 130° C.for 10-12 hours.

-   M_(w) (GPC, PMMA calibration)=645,000 g/mol-   η_(sp)/c (CHCl₃, 20° C.)=48.9 ml/g-   Thickening action (4.5% by weight in a 150 N oil): 12.84 mm²/s

Example 4 Preparation of a Copolymer of Behenyl Acrylate and n-ButylMethacrylate P4

In a three-necked flask equipped with a sabre stirrer and a refluxcondenser, 229.5 g of behenyl acrylate (e.g. 45% behenyl acrylate fromSidobre Sinova), 25.5 g of n-butyl methacrylate (manufacturer: Röhm), 45g of 100 N oil and 0.255 g of dodecylmercaptan are heated to 80° C. 0.48g of t-butyl perpivalate and 0.29 g of t-butyl perbenzoate aresubsequently added, in order to initiate the polymerization. 2 hoursafter reaching the peak temperature, 0.60 g of t-butyl perbenzoate areadded and polymerization is continued at 130° C. for 10-12 hours.

-   M_(w) (GPC, PMMA calibration)=474,000 g/mol-   η_(sp)/c (CHCl₃, 20° C.)=52.1 ml/g-   Thickening action (4.5% by weight in a 150 N oil):

13.09 mm²/s

Example 5 Preparation of a Copolymer of Behenyl Acrylate and IsononylMethacrylate P5

In a three-necked flask equipped with a sabre stirrer and a refluxcondenser, 229.5 g of behenyl acrylate (e.g. 45% behenyl acrylate fromSidobre Sinova), 25.5 g of isononyl methacrylate (e.g. the methacrylateof isononyl alcohol from Oxeno Olefinchemie GmbH, Marl prepared by meansof transesterification starting from methyl methacrylate), 45 g of 100 Noil and 0.255 g of dodecylmercaptan are heated to 80° C. 0.48 g oft-butyl perpivalate and 0.29 g of t-butyl perbenzoate are subsequentlyadded, in order to initiate the polymerization. 2 hours after reachingthe peak temperature, 0.60 g of t-butyl perbenzoate are added andpolymerization is continued at 130° C. for 10-12 hours.

-   M_(w) (GPC, PMMA calibration)=503,000 g/mol-   η_(sp)/c (CHCl₃, 20° C.)=48.1 ml/g-   Thickening action (4.5% by weight in a 150 N oil): 13.12 mm²/s

Example 6 Preparation of Poly(C₁₆₋₁₈-Alkyl Methacrylate) P6

In a three-necked flask equipped with a sabre stirrer and a refluxcondenser, 5.0 g of 10 N oil are initially charged under a nitrogenprotective gas atmosphere and heated to 120° C. A mixture of 113.6 g ofC₁₆₋₁₈-alkyl methacrylate (e.g. the methacrylate of TA1618E alcohol fromProcter & Gamble prepared by means of transesterification starting frommethyl methacrylate), 17.4 g of 100 N oil, 0.56 g of t-butylper-2-ethylhexanoate and 0.12 g of dodecylmercaptan are subsequentlymetered in within 60 minutes. After 0.5 hours, a further 0.75 g oft-butyl per-2-ethylhexanoate is added and polymerization is continuedfor 10-12 hours. After the end of the polymerization, the mixture isdiluted with 264.0 g of 100 N oil.

-   Thickening action (15% by weight in a 150 N oil): 12.83 mm²/s

Example 7 Preparation of a Poly(C₁₂₋₁₈-Alkyl Methacrylate) P7

In a polymerization vessel, 1350 kg of C₁₆₋₁₈-alkyl methacrylate (e.g.the methacrylate of the alcohol TA1618E from Procter & Gamble preparedby means of transesterification starting from methyl methacrylate), 3150kg of C₁₂₋₁₄-alkyl methacrylate (e.g. the methacrylate of the alcoholLorol Spezial from Cognis prepared by means of transesterificationstarting from methyl methacrylate), 1125 kg of 100 N oil and also 1.9 kgof dodecylmercaptan are initially charged and the mixture is heated to120° C. A solution of 4 kg of t-butyl per-2-ethylhexanoate in 200 kg of100 N oil is prepared and added to the monomer mixture in threesuccessive metering steps. In the first step, initiator is added at ametering rate of 40 kg/h over 1 hour, and in the second step at ametering rate of 60 kg/h over a period of 40 minutes. 4.5 kg of t-butylper-2-ethylhexanoate are dissolved in the remaining initiator solutionand the resulting solution is added at a metering rate of 164 kg/hwithin 45 minutes. Polymerization is allowed to continue for approx. 1hour.

Example 8 Preparation of Poly(C₁₂₋₁₈-Alkyl Methacrylate) P8

In a three-necked flask equipped with a sabre stirrer and refluxcondenser, 17.8 g of C₁₂₋₁₈-alkyl methacrylate (e.g. based on a 78:22mixture of the methacrylates of the alcohol Neodol 25E from ShellChemicals and the alcohol TA1618E from Procter & Gamble, each preparedby means of transesterification starting from methyl methacrylate) andalso 160 g of 100 N oil are initially charged under a nitrogenprotective gas atmosphere and heated to 85° C. 1.8 g of t-butylper-2-ethylhexanoate are then added, in order to initiate thepolymerization. At the same time, metering in of a mixture of 622.2 g ofC₁₂₋₁₈-alkyl methacrylate and 1.6 g of t-butyl per-2-ethylhexanoate iscommenced and this is continued for 3.5 hours. After a further 2 hours,further polymerization is effected using 1.28 g of t-butylper-2-ethylhexanoate at 85° C. for 10-12 hours. After the end of thepolymerization, the mixture is diluted with 800 g of 100 N oil.

-   Thickening action (10% in a 150 N oil): 16.31 mm²/s

Example 9 Filtration Volumes in ml from a Deparaffinization Study Usinga 600N Feedstock of a European Refinery Using Novel Styrenic Copolymers

-   Solvent system: n-heptane-   Feedstock: solvent ratio=1:2-   Procedure 1) mixing at 70° C., 2) 30 min in a bath at 25° C., 3) 60    min in a bath at −30° C.

Filtration temperature: −30° C. Filtration P6 P6 P7 P7 P8 P8 time No(800 ppm) + P1 (800 ppm) + C1 (1370 ppm) + P1 (1370 ppm) + C1 (1230ppm) + P1 (1230 ppm) + C1 [s] additive (300 ppm) (300 ppm) (200 ppm)(200 ppm) (200 ppm) (200 ppm) 0 0 0 0 0 0 0 0 10 1 7 3 9 6 5 2 20 2 9 148 9 3 30 2 10 8 17 11 10 4 40 3 11 9 19 13 12 5 50 3.5 12 9 21 14 13.5 660 4 13 9.5 23 15 14.5 7 70 5 14 10 24.5 17 15.5 8 80 5.5 15 10.5 26 1816.5 9 90 6.5 16 11 27.5 19 17.5 9.5 100 7 16.5 11 28 20 18 10 120 8 1812 30.5 22 20 10 140 8.5 19.5 12.5 33 23.5 21 11 160 9.5 21 13 36 2522.5 11 180 10 22 14 37.5 27 23.5 12 200 10 23.5 15 39.5 28 25 12.5 24011 25 16 42.5 30 27 13 300 12 28.5 18 47.5 34 30 15 600 16 39 24.5 69.547 41 20

Example 10 Filtration Volumes in ml from a Deparaffinization Study Usinga 500N Feedstock of a Thai Refinery

-   Solvent system: n-heptane-   Feedstock: solvent ratio=1:2-   Procedure: 1) mixing at 70° C., 2) 30 min in a bath at 25° C., 3) 90    min in a bath at −30° C.

Filtration temperature: −30° C. Filtra- No P6 P7 P6 tion addi- (800ppm) + P1 (1370 ppm) + P1 (800 ppm) + C1 time [s] tive (300 ppm) (200ppm) (300 ppm) 0 0 0 0 0 100 8.5 18 19 16 200 11 24.5 27 22 300 12.5 3032 26.5 420 14 35 38 31 480 15 38 40 33 600 16.5 42 45 37 720 17.5 46 4940 840 18.5 50 53 42.5 900 19.5 52.5 55 44

Example 11 Filtration Volumes in ml from a Deparaffinization Study Usinga 300N Feedstock from a Refinery in South America

-   Solvent system: 55% of methyl ethyl ketone/45% of toluene-   Feedstock: solvent ratio=1:3-   Procedure: 1) mixing at 70° C., 2) 30 min in a bath at 25° C., 3) 60    min in a bath at −18° C.

Filtration temperature: −18° C. Filtration time No P6 (800 ppm) + P1 P6(800 ppm) + C1 [s] additive (150 ppm) (400 ppm) 0 0 0 0 50 17 38 31 10024 55 45 150 29 68 56

Example 12 Filtration Volumes in ml from a Deparaffinization Study Usinga 600N Feedstock from a European Refinery with Novel Copolymers

-   Solvent system: n-heptane-   Feedstock: solvent ratio=1:2-   Procedure: 1) mixing at 70° C., 2) 30 min in a bath at 25° C., 3) 60    min in a bath at −30° C.

Filtration temperature: −30° C. Filtration C1 P1 P2 P4 P5 time No (300(300 (300 (300 (300 [s] additive ppm) ppm) ppm) ppm) ppm) 0 0 0 0 0 0 010 1 1 3 1 3.5 2 20 2 1 4.5 2 4.5 3.5 30 2 1.5 5.5 2.5 5.5 5 40 3 2 6.53.5 6.5 6 50 3.5 2.5 8 4.5 7.5 7 60 4 3 9 6 8.5 8 70 5 3.5 9 7 9.5 8.580 5.5 4 10 8 10 9 90 6.5 4.5 10.5 8.5 10 9.5 100 7 5 11 8.5 10 9.5 1208 5.5 12 9.5 11 10 140 8.5 6 13 10 11.5 10 160 9.5 6.5 14 10 12 11 18010 7 14.5 10.5 13 11.5 200 10 7.5 15 11 14 12 240 11 8 17 12 15 13 30012 9 18.5 13 16.5 14 600 16 12 26 18 23 19.5

Comparative Example Preparation of a Polybehenyl Acrylate C1

In a three-necked flask equipped with a sabre stirrer and a refluxcondenser, 255 g of behenyl acrylate (e.g. based on 45% behenyl acrylatefrom Sidobre Sinova), 45 g of 100 N oil and 0.13 g of dodecylmercaptanare initially charged under a nitrogen protective gas atmosphere andheated to 80° C. 0.41 g of t-butyl perpivalate and 0.25 g of t-butylperbenzoate are subsequently added, in order to initiate thepolymerization. 2 hours after reaching the peak temperature, 0.51 g oft-butyl perbenzoate are added, after which polymerization is continuedat 130° C. for 10-12 hours.

-   η_(sp)/c (CHCl₃, 20° C.)=42 ml/g-   Thickening action (4.5% by weight in a 150 N oil): 12.19 mm²/s

1. A copolymer which is suitable for preparing additives for solvent deparaffinization of paraffinic mineral oil distillates, and which is polymerized from free-radically polymerizable monomers of the following formulae A and B:

where R¹═H or CH₃, R²=phenyl, benzyl, naphthyl, anthranyl, phenanthryl, N-pyrrolidonyl, N-imidazolyl, 2-pyridyl, 4-pyridyl or an alkyl-substituted aromatic substituent or R²═COOR³ where R³═H or R³ is a linear or branched alkyl radical of C₁-C₁₀ or R³ is a heteroatom-substituted radical —(CH₂)_(n)X where X═OH or X═N(R⁴)₂ where n=1-10 and R⁴ is in each case independently H or R⁴═C₁-C₄-alkyl or R³ is —(CH₂CH₂O)_(m)R⁵ where m=1-90 and R⁵═H or R⁵═C₁-C₁₈ or R³ is a benzyl, phenyl or cyclohexyl radical or R²═CONHR⁶ where R⁶═H or R⁶ is a linear or branched alkyl radical of C₁-C₁₀ or R⁶ is a heteroatom-substituted radical —(CH₂)_(n)X where X═OH or X═N(R⁴)₂ where n=1-10 and R⁴ is in each case independently H or R⁴═C₁-C₄-alkyl;

where R⁷═H or CH₃ and the R⁸ radical=linear or branched alkyl radicals of C₁₂-C₄₀.
 2. The copolymer according to claim 1, wherein the proportion by weight of the monomer A in the total weight of the copolymer is 0.1-70%.
 3. The copolymer according to claim 1, wherein at least 50% of the monomers B contain alkyl radicals R⁸ of chain length greater than or equal to C₁₆.
 4. The copolymer according to claim 1, wherein the monomers of formula A consist of one or more monomers selected from styrene, butyl methacrylate, methyl methacrylate or 2-ethylhexyl methacrylate.
 5. A polymer mixture comprising one or more copolymers according to claim 1, and one or more further homo- or copolymers which are polyalkyl methacrylates and have alkyl substituents of chain length C₁-C₂₄.
 6. The polymer mixture according to claim 5, wherein the further homo- or copolymers have alkyl substituents of chain length C₁₂-C₁₈.
 7. The polymer mixture according to claim 5, wherein the ratio of the copolymers and the further homo- or copolymers is 1:20 to 20:1.
 8. The polymer mixture according to claim 5, wherein the further homo- or copolymer is a polyalkyl methacrylate which contains up to 20% by weight of C₁-C₁₀ methacrylates.
 9. The polymer mixture according to claim 5, wherein the molecular weight of the polymers used, is between 10,000 and 3,000,000 g/mol.
 10. A process for preparing the polymer components according to claim 5, in a manner known per se in a batch process by introducing all of the monomers used into the initial charge, or in a feed process by synthesizing at least one of the polymers of the polymer mixture using an increased concentration of at least one of the monomers used in the initial monomer charge in comparison to the other monomer types used with the aim of preparing a polymer mixture in which different polymers are present with regard to the monomer composition.
 11. A dewaxing additive comprising the copolymer according to claim 1, and, optionally, further customary dewaxing additives.
 12. The dewaxing additive according to claim 11, wherein the dewaxing additive is a solution of the copolymer in an oil of the paraffinic or naphthenic type, or in an organic solvent.
 13. The dewaxing additive according to claim 12, wherein the organic solvent is toluene, xylene and/or naphtha.
 14. A method for solvent deparaffinization of paraffinic mineral oil distillates, comprising adding a dewaxing additive according to claim 11, to a dewaxing process.
 15. The method according to claim 14, wherein the addition rate of the copolymer in the dewaxing process is 0.005-0.5%.
 16. A dewaxing additive comprising the polymer mixture according to claim 5, and, optionally, further customary dewaxing additives.
 17. The dewaxing additive according to claim 16, wherein the dewaxing additive is a solution of the polymer mixture in an oil of the paraffinic or naphthenic type, or in an organic solvent.
 18. The dewaxing additive according to claim 17, wherein the organic solvent is toluene, xylene and/or naphtha.
 19. A method for solvent deparaffinization of paraffinic mineral oil distillates, comprising adding a dewaxing additive according to claim 16, to a dewaxing process.
 20. The method according to claim 19, wherein the addition rate of the polymer mixture in the dewaxing process is 0.005-0.5%. 